Spatial routing among microwave backhaul transceivers

ABSTRACT

A first microwave backhaul transceiver may comprise a plurality of antenna elements. The transceiver may determine atmospheric conditions between it and one or more potential link partners, and adjust a radiation pattern of the plurality of antenna elements based on the determined atmospheric conditions. A first radiation pattern of the plurality of antenna elements may correspond to a first microwave backhaul link between the first microwave transceiver and a second microwave backhaul transceiver. A second radiation pattern of the plurality of antenna elements may correspond to a second microwave backhaul link between the first microwave transceiver and a third microwave backhaul transceiver. The transceiver may adjust the radiation pattern based on characteristics of data to be transmitted, and based on a routing table it maintains.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.14/248,992 filed Apr. 9, 2014 (now U.S. Pat. No. 9,338,661), which alsoclaims priority to and the benefit of the following application(s), eachof which is hereby incorporated herein by reference:

U.S. provisional patent application 61/809,935 titled “MicrowaveBackhaul” filed on Apr. 9, 2013;

U.S. provisional patent application 61/881,016 titled “MicrowaveBackhaul Methods and Systems” filed on Sep. 23, 2013; and

U.S. provisional patent application 61/884,765 titled “MicrowaveBackhaul Methods and Systems” filed on Sep. 23, 2013.

INCORPORATION BY REFERENCE

The entirety of each of the following applications is herebyincorporated herein by reference:

United States patent publication 2014/0003559 titled “Method and SystemFor Improved Cross Polarization Rejection And Tolerating CouplingBetween Satellite Signals” filed on Jul. 2, 2013.

BACKGROUND

Limitations and disadvantages of conventional approaches to microwavebackhaul will become apparent to one of skill in the art, throughcomparison of such approaches with some aspects of the present methodand system set forth in the remainder of this disclosure with referenceto the drawings.

BRIEF SUMMARY

Methods and systems are provided for spatial routing among microwavebackhaul transceivers, substantially as illustrated by and/or describedin connection with at least one of the figures, as set forth morecompletely in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example microwave backhaul link between a firstmicrowave backhaul transceiver and a second microwave backhaultransceiver.

FIG. 2 shows an example implementation of a steerable microwave backhaultransceiver.

FIG. 3 shows an example implementation of the subassembly of FIG. 2.

FIG. 4A shows a first example implementation of the circuitry of FIG. 3.

FIG. 4B shows a second example implementation of the circuitry of FIG.3.

FIG. 5A shows an example configuration of the beamforming circuitry ofFIG. 4A.

FIG. 5B shows an example configuration of beamforming components of thedigital signal processing circuitry of FIG. 4B.

FIGS. 6A-6B illustrate spatial routing for maximizing throughput.

FIGS. 7A-7C illustrate spatial routing for minimizing latency.

FIG. 8 illustrates spatial routing for avoiding collisions amongbackhaul links.

DETAILED DESCRIPTION

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (i.e. hardware) and any software and/orfirmware (“code”) which may configure the hardware, be executed by thehardware, and or otherwise be associated with the hardware. As usedherein, for example, a particular processor and memory may comprise afirst “circuit” when executing a first one or more lines of code and maycomprise a second “circuit” when executing a second one or more lines ofcode. As utilized herein, “and/or” means any one or more of the items inthe list joined by “and/or”. As an example, “x and/or y” means anyelement of the three-element set {(x), (y), (x, y)}. As another example,“x, y, and/or z” means any element of the seven-element set {(x), (y),(z), (x, y), (x, z), (y, z), (x, y, z)}. As utilized herein, the terms“e.g.,” and “for example” set off lists of one or more non-limitingexamples, instances, or illustrations. As utilized herein, circuitry is“operable” to perform a function whenever the circuitry comprises thenecessary hardware and code (if any is necessary) to perform thefunction, regardless of whether performance of the function is disabled,or not enabled, by some user-configurable setting. As used herein,“microwave” frequencies range from approximately 300 MHz to 300 GHz and“millimeter wave” frequencies range from approximately 30 GHz to 300GHz. Thus, the “microwave” band includes the “millimeter wave” band.

FIG. 1 depicts an example microwave backhaul link between a firstmicrowave backhaul transceiver and a second microwave backhaultransceiver. Shown are a tower 108 to which access network antennas 112and remote radio head (RRH) 110 are attached, a baseband unit 104, atower 122 a to which microwave backhaul transceiver 120 a (comprisingsubassembly 114 a and reflector 116 a) is attached, and a tower 122 b towhich microwave backhaul transceiver 120 b (comprising subassembly 114 band reflector 116 b) is attached. At any particular time, there may beone or more active (i.e., carrying traffic or synchronized and ready tocarry traffic after a link setup time that is below a determinedthreshold) links 106 (shown as wireless, but may be wired or optical)between the RRH 110 and the BBU 104. At any particular time, there maybe one or more active backhaul links 118 between the pair of backhaultransceivers 120 a and 120 b and/or between one of the transceivers 120a and another one or more backhaul transceivers not shown.

The antennas 112 are configured for radiating and capturing signals ofan access network (e.g., 3G, 4G LTE, etc. signals to/from mobilehandsets). Although the example pair of microwave transceivers 120 a and120 b are used for backhauling cellular traffic, this is just oneexample type of traffic which may be backhauled by microwavetransceivers, such as 120 a and 120 b, that implement aspects of thisdisclosure.

For an uplink from a mobile handset to the core network 102, theantennas 112 receive signals from the handset and convey them to the RRH110. The RRH 110 processes (e.g., amplifies, downconverts, digitizes,filters, and/or the like) the signals received from the antennas 112 andtransmits the resulting signals (e.g., downconverted I/Q signals) to thebaseband unit (BBU) 104 via link(s) 106. The BBU 104 processes, asnecessary, (e.g., demodulates, packetizes, modulates, and/or the like)the signals received via link(s) 106 for conveyance to the microwavebackhaul transceiver 120 a via link 113 a (shown as wired or optical,but may be wireless). The microwave backhaul transceiver 120 aprocesses, as necessary (e.g., upconverts, filters, beamforms, and/orthe like), the signals from BBU 104 for transmission via the subassembly114 a and reflector 116 a over microwave backhaul link(s) 118. Themicrowave transceiver 120 b receives the microwave signals overmicrowave backhaul link(s) 118 via the subassembly 114 b and reflector116 b, processes the signals as necessary (e.g., downconverts, filters,beamforms, and/or the like) for conveyance to the cellular serviceprovider core network 102 via link 113 b.

For a downlink from the core network 102 to the mobile handset, datafrom the core network 102 is conveyed to microwave backhaul transceiver120 b via link 113 b. The transceiver 120 b processes, as necessary(e.g., upconverts, filters, beamforms, and/or the like), the signalsfrom the core network 102 for transmission via the subassembly 114 b andreflector 116 b over link(s) 118. Microwave transceiver 120 a receivesthe microwave signals over the microwave backhaul link(s) 118 via thesubassembly 114 a and reflector 116 a, and processes the signals asnecessary (e.g., downconverts, filters, beamforms, and/or the like) forconveyance to the BBU 104 via link 113 a. The BBU 104 processes thesignal from transceiver 120 a as necessary (e.g., demodulates,packetizes, modulates, and/or the like) for conveyance to RRH 110 vialink(s) 106. The RRH 110 processes, as necessary (e.g., upconverts,filters, amplifies, and/or the like), signals received via link 106 fortransmission via an antenna 112.

FIG. 2 shows an example implementation of a steerable microwave backhaultransceiver. The depicted transceiver 120 represents each of thetransceivers 120 a and 120 b described above with reference to FIG. 1.The example transceiver 120 comprises the subassembly 114 mounted to asupport structure 204 (which may, in turn, mount the assembly to themast/tower 122, building, or other structure, not shown in FIG. 2), anda link 113 which represents each of the links 113 a and 113 b. Thesubassembly 202 comprises an antenna array 202 which in turn comprises aplurality of antenna elements. The subassembly 202 may be mounted suchthat the antenna elements are positioned at or near a focal plane of thereflector 116. The subassembly may comprise, for example, one or moresemiconductor dies (“chips”) arranged on one or more printed circuitboards. The antenna elements may be, for example, horns and/ormicrostrip patches. In the example implementation depicted, the antennaelements capture signals reflected by reflector 116 for reception andbounce signals off the reflector 116 for transmission. The radiationpattern 208 of the antenna array 202 corresponds to a radiation pattern206 after reflection off the reflector 116. Although the radiationpatterns may comprise multiple lobes, only a main lobe is shown forsimplicity of illustration. In another implementation, the antennaelements may directly receive backhaul signals, or receive them througha lens, for example.

FIG. 3 shows an example implementation of the subassembly of FIG. 2. Theexample subassembly 114 comprises four feed horns 306 ₁-306 ₄, andcircuitry (e.g., a chip or chipset) 302. The circuitry 302 drivessignals to the horns 306 ₁-306 ₄ via one or more of feed lines 304 ₁-304₈ for transmission, and receives signals from the horns 306 ₁-306 ₄ viafeed lines 304 ₁-304 ₈ for reception. The circuitry 302 is operable tocontrol the phases and/or amplitudes of signals output to the feed lines304 ₁-304 ₈ so as to achieve desired transmit radiation patterns.Similarly, the circuitry 302 is operable to control the phases and/oramplitudes of signals received from the feed lines 304 ₁-304 ₈ so as toachieve desired receive radiation patterns.

The feed lines 304 ₁-304 ₄ correspond to a first polarization and thefeed lines 304 ₅-304 ₈ correspond to a second polarization. Accordingly,the subassembly 114 may be operable to concurrently receive twodifferent signals on the same frequency but having differentpolarizations, concurrently transmit two different signals on the samefrequency but having different polarizations, and/or concurrentlytransmit a first signal having a first polarization and receive a secondsignal having a second polarization. Furthermore, the radiation patternfor the two polarizations may be controlled independently of oneanother. That is two independent sets of amplitude and phase beamformingcoefficients may be maintained by circuitry 302 as, for example,described below with reference to FIGS. 5A-5B.

FIGS. 4A and 4C show a first example implementation of the circuitry ofFIG. 3. In the example implementation shown, the circuitry 302 comprisesanalog front-ends 402 ₁-402 ₈, a beamforming circuit 404,analog-to-digital converter (ADC) 406, one or more sensors 414, digitalcircuitry 408, and a digital-to-analog converter (DAC) 440. Thecircuitry 302 outputs received data onto link 113 (e.g., coaxial cable)and receives to-be-transmitted data via link 113.

The sensor(s) 414 may be operable to determine movement, orientation,geographic position, and/or other physical characteristics of thetransceiver 120. Accordingly, the sensor(s) 414 may comprise, forexample, a gyroscope, an accelerometer, a compass, a GPS receiver,and/or the like. Additionally or alternatively, the sensor(s) 414 may beoperable to determine atmospheric conditions and/or other physicalobstructions between the transceiver 120 and potential microwavebackhaul link partners. Accordingly, the sensor(s) 414 may comprise, forexample, a hygrometer, a psychrometer, and/or a radiometer. Thesensor(s) 414 may output readings/measurements as signal 415.

For receive operations, each front-end circuit 402 _(n) (1≦n≦N, whereN=8 in the example implementation depicted) is operable to receive amicrowave signal via feed line 304 _(n). The front-end circuit 402 _(n)processes the signal on feed line 304 _(n) by, for example, amplifyingit via low noise amplifier LNA 420 _(n), filtering it via filter 426_(n), and/or downconverting it via mixer 424 _(n) to an intermediatefrequency or to baseband. The local oscillator signal 431 _(n) for thedownconverting may be generated by the circuit 404, as described below.The result of the processing performed by each front-end circuit 402_(n) is a signal 403 _(n).

The ADC 406 is operable to digitize signal 405 to generate signal 407.The bandwidth of the ADC 406 may be sufficient such that it canconcurrently digitize entire microwave backhaul bands comprising aplurality of channels or sub-bands (e.g., the ADC 406 may have abandwidth of 1 GHz or more).

The DAC 440 is operable to convert digital signal 439 (e.g., a digitalbaseband signal) to an analog signal 441.

For receive, the digital circuitry 408 is operable to process thedigital signals 407 for output to link 113. The processing may include,for example, symbol-to-bits demapping, FEC decoding, deinterleaving,equalizing, and/or the like. The processing may include, for example,performing an interference (e.g., cross-polarization interference)cancellation process such as is described in, for example, theabove-incorporated U.S. patent application Ser. No. 13/933,865. Theprocessing may include, for example, channelization to select, foroutput to the link 113, sub-bands or channels of the signal 407. Theprocessing may include, for example, band stacking, channel stacking,band translation, and/or channel translation to increase utilization ofthe available bandwidth on the link 113.

For transmit, the digital circuitry 408 is operable to perform digitalbaseband processing for preparing data received via link 113 to betransmitted via the microwave backhaul link(s) 118. Such processing mayinclude, for example, processing of packets received via the link 113 torecover the payload data from such packets, and then packetization,modulation, etc. to generate a microwave backhaul digital basebandsignal 439 carrying the payload data.

For transmit and receive, the digital circuitry 408 may determine whichother microwave backhaul transceiver(s) to which to listen based on arouting table 442 that has entries for other microwave backhaultransceivers and which is maintained in accordance with one or morespatial routing algorithms. Thus, rather than having fixed communicationpartners and fixed communication parameters (bandwidth, modulationorder, FEC code word length, and/or the like) designed to handleworst-case conditions, microwave backhaul transceivers in accordancewith this disclosure may be operable to take advantage of the fact thatmost of the time worst-case conditions are not present and, therefore,parameters may be adjusted to increase range, increase throughput,decrease latency, decrease power consumption, and/or the like duringnon-worst-case conditions.

The beamforming circuit 404 comprises local oscillator synthesizer 428operable to generate a reference local oscillator signal 429, andcomprises phase shift circuits 430 ₁-430 _(N) operable to generate Nphase shifted versions of signal 429, which are output as signals 431₁-431 _(N). The amount of phase shift introduced by each of the circuits430 ₁-430 _(N) may be determined by a corresponding one of a pluralityphase coefficients. The plurality of phase coefficients may becontrolled to achieve a desired radiation pattern of the antennaelements 306 ₁-306 ₄. In another example implementation, additionalfront-end circuits 402 and phase shifters 430 may be present to enableconcurrent reception of additional signals via the antenna elements 306₁-306 _(N).

The beamforming circuit 404 also comprises a circuit 432 which isoperable to perform weighting of the signals 403 ₁-403 ₈ by theirrespective amplitude coefficients determined for the desired radiationpattern. For reception, the circuit 432 is operable to combine theweighted signals prior to outputting them on signal 405.

In an example implementation, the phase and/or amplitude coefficientsmay be controlled/provided by the digital circuitry 408 via signal 416.The phase and amplitude coefficients may be adjusted dynamically. Thatis, the coefficients may be adjusted while maintaining one or moreactive backhaul links.

Dynamically adjusting the phase and/or amplitude coefficients duringreception of energy of microwave backhaul signals results incorresponding changes in the radiation pattern of the transceiver 120.Different patterns may capture different amounts of energy fromdifferent microwave backhaul signals. By adjusting the radiation patternintelligently, sufficient energy from multiple beams may be capturedduring a single time interval such that content carried in each of thebeams during that time interval can be demodulated and decoded with lessthan a threshold amount of errors. In other words, the “scanning” mayeffectively enable “illuminating” more of the reflector 116 than could asingle antenna element having the same dimensions as the overalldimensions of the array of antenna elements 306. As an example toillustrate, for a first radiation pattern (i.e., first set of phase andamplitude coefficients), energy received from a first microwave backhaulsignal may be above a threshold, but energy received from a secondmicrowave backhaul signal may be below the threshold. Conversely, for asecond radiation pattern, power received from the first microwavebackhaul signal may be below the threshold, but power received from thesecond microwave backhaul signal may be above the threshold.Accordingly, by dwelling on each of the two radiation patterns for asufficient percentage of a sufficiently short time interval, sufficientenergy may be captured for each of the microwave backhaul signals duringthat time interval such that the information on both microwave backhaulsignals during that time interval can be recovered.

In an example implementation, the sensor(s) 414 may indicate atmosphericconditions through which microwave backhaul signals to and/or from thetransceiver 120 may travel. The digital circuitry 408 may make spatialrouting decisions based on the atmospheric conditions. That is, thedigital circuitry 408 may determine which other microwave backhaultransceiver to communicate with based on the atmospheric conditions andconfigure the phase and/or amplitude coefficients accordingly to achievea radiation pattern that supports communication with the determinedother microwave backhaul assembly. This may improve performance of thenetwork in the presence of rain, snow, fog, smog, or other atmosphericconditions which negatively impact microwave communications.

In an example implementation, the sensor(s) 414 may indicate physicalobstructions (which may include atmospheric conditions such as rainand/or other obstructions such as vehicles, animals, structures, etc.)which may impede microwave backhaul signals to and/or from thetransceiver 120. The digital circuitry 408 may make spatial routingdecisions based on the presence or absence of physical obstructions.That is, the digital circuitry 408 may determine which other microwavebackhaul transceiver to communicate with based on the physicalobstructions and configure the phase and/or amplitude coefficientsaccordingly to achieve a radiation pattern that supports communicationwith the determined other microwave backhaul assembly.

In an example implementation, the phase and/or amplitude beamformingcoefficients may be controlled based on data retrieved from a localand/or networked database. Such data may include, for example, dataindicating geographical locations of other microwave backhaul assemblieswith which the transceiver 120 may desire to establish a microwavebackhaul link, and/or data indicating atmospheric conditions which mayimpact microwave communications. Such data may, for example, be used forpopulating routing tables and/or spatial routing algorithms in thedigital circuitry 408.

The implementation of circuitry 302 shown in FIG. 4A may be realized onany combination of one or more semiconductor (e.g., Silicon, GaAs) diesand/or one or more printed circuit board. For example, each front-endcircuit 402 _(n) may comprise one or more first semiconductor dieslocated as close as possible to (e.g., a few centimeters from) itsrespective antenna element 306 _(N), the circuits 404 and 406 maycomprise one or more second semiconductor dies on the same PCB as thefirst die(s), the circuits 408 and 440 may reside on one or more thirdsemiconductor dies on the same PCB, and the sensor(s) 414 may bediscrete components connected to the PCB via wires or wirelessly.

FIG. 4B depicts a second example implementation of the circuitry 302. Inthis example implementation, the application of beamforming amplitudeand phase coefficients is performed in the digital domain in digitalcircuitry 408. That is, in addition to other functions performed bydigital circuitry 408 (such as those described above), the digitalcircuitry may also perform phase and amplitude weighting and combiningof the signals 413 ₁-413 ₈.

Each of the circuits 450 ₁-450 ₈ is operable to performdigital-to-analog conversion (when used for transmission) and/oranalog-to-digital conversion (when used for reception). In this regard,for reception, the signals 413 ₁-413 ₈ are the result of digitization ofthe signals 403 ₁-403 ₈ output by the front-ends 402 ₁-402 ₈. Fortransmission, the signals 413 ₁-413 ₈ are the result of digitalcircuitry 408 performing phase and amplitude weighting and combining ofone or more digital baseband signals (the weighting and combining may beas described in FIG. 5B, for example).

The implementation of circuitry 302 shown in FIG. 4B may be realized onany combination of one or more semiconductor (e.g., Silicon, GaAs) diesand/or one or more printed circuit board. For example, each pair of 402_(n) and 450 _(n) may comprise an instance of a first semiconductor dieand may be located as close as possible to (e.g., a few centimetersfrom) its respect antenna element 306 _(n), the digital circuitry 408may comprise an instance of a second semiconductor die on the same PCBas the first dies, and the sensor(s) 414 may be discrete componentsconnected to the PCB via wires or wirelessly.

Referring now to FIG. 5A, there is shown an example implementation ofthe circuit 232 that supports spatial routing of a full-duplex microwavebackhaul link. In the example implementation shown, the signals 403₁-403 ₄ correspond to a received signal having a first polarization(e.g., horizontal) and the signals 403 ₅-403 ₈ correspond to a signal tobe transmitted with a second polarization (e.g., vertical).

In the receive direction, each of the signals 403 ₁-403 ₄ has beenreceived via a respective one of antenna elements 306 ₁-306 ₄, and hadits phase shifted, during downconversion by a respective one of mixers402 ₁-402 ₄, by a respective phase coefficient of a selected first setof coefficients. In circuit 232, the amplitude of each of signals 403₁-403 ₄ is scaled by a respective amplitude coefficient of the selectedfirst set of coefficients. The weighted signals are summed resulting insignal 405. The signal 405 thus corresponds to a received signal using aradiation pattern corresponding to the selected first set of phase andamplitude coefficients.

In the transmit direction, the signal 441 is split into four signals,each of which has its amplitude scaled by a respective amplitudecoefficient of a selected second set of coefficients. The result of theamplitude scaling is signals 403 ₅-403 ₈. The signals 403 ₅-403 ₈ areconveyed to front-ends 402 ₅-402 ₈ where, during upconversion tomicrowave frequency, each is phase shifted by a respective phasecoefficient of the selected second set of coefficients. The upconvertedsignals are then conveyed, via feed lines 304 ₅-304 ₈, to antennaelements 306 ₁-306 ₄ for transmission.

For both transmitting and receiving with the same link partner on thesame frequency, the first set of phase and amplitude coefficients is thesame as the second set of phase and amplitude coefficients. This may beachieved by storing a single set of coefficients and providing the sameset to both scaling circuits 502 ₁-502 ₄ and 502 ₅-502 ₈.

For transmitting to a first link partner while receiving from a secondlink partner on the same frequency, the first set of phase and amplitudecoefficients is the different than the second set of phase and amplitudecoefficients. This may be achieved by storing two sets of coefficientsand providing the first set to circuits 502 ₁-502 ₄ and the second setto circuits 502 ₅-502 ₈. This enables independently adjusting the twosets of coefficients which corresponds to independently steering thetransmit and receive radiation patterns.

Referring now to FIG. 5B, there is shown an example implementationdigital circuitry that supports spatial routing of a full-duplexmicrowave backhaul link. In the example implementation shown, thesignals 413 ₁-413 ₄ correspond to a received signal having a firstpolarization (e.g., horizontal) and the signals 413 ₅-413 ₈ correspondto a signal to be transmitted with a second polarization (e.g.,vertical).

In the receive direction, each of the signals 413 ₁-413 ₄ has beenreceived via a respective one of antenna elements 306 ₁-306 ₄,downconverted by a respective one of mixers 402 ₁-402 ₄, and digitizedby a respective one of circuits 450 ₁-4504. The circuits 504 ₁-504 ₄scale the amplitudes of the signals 403 ₁-403 ₄ by respective amplitudecoefficients of a selected first set of coefficients. The circuits 504₁-504 ₄ also phase shift the signals 403 ₁-403 ₄ by respective phasecoefficients of the selected first set of coefficients. The resultingphase-shifted and amplitude-scaled signals are then combined to generatesignal 508. The signal 508 thus corresponds to a received signal using aradiation pattern corresponding to the selected first set of phase andamplitude coefficients.

In the transmit direction, the signal 510 is split into four signals.Each of the circuits 504 ₅-504 ₈ scales a respective one of the signals413 ₅-413 ₈ by a respective amplitude coefficient of a selected secondset of coefficients. Each of the circuits 504 ₅-504 ₈ shifts a phase ofa respective one of the signals 413 ₅-413 ₈ by a respective phasecoefficient of the selected second set of coefficients. The result ofthe amplitude scaling is signals 403 ₅-403 ₈. The signals 403 ₅-403 ₈are conveyed to circuits 450 ₅-450 ₈ where they are converted to analogsignals 403 ₅-403 ₈. The signals 403 ₅-403 ₈ are then upconverted byfront-ends 402 ₅-402 ₈ and then conveyed, via feed lines 304 ₅-304 ₈, toantenna elements 306 ₁-306 ₄ for transmission.

For both transmitting and receiving with the same link partner on thesame frequency, the first set of phase and amplitude coefficients may bethe same as the second set of phase and amplitude coefficients. This maybe achieved by storing a single set of coefficients and providing thesame set to both scaling circuits 504 ₁-504 ₄ and 504 ₅-504 ₈.

For transmitting to a first link partner while receiving from a secondlink partner on the same frequency, the first set of phase and amplitudecoefficients may be different than the second set of phase and amplitudecoefficients. This may be achieved by storing two sets of coefficientsand providing the first set to circuits 504 ₁-504 ₄ and the second setto circuits 504 ₅-504 ₈. This enables independently adjusting the twosets of coefficients which corresponds to independently steering thetransmit and receive radiation patterns.

Although the example implementations in FIGS. 5A and 5B use differentpolarizations to enable concurrent transmission and reception on thesame frequencies, other implementations may use different frequenciesfor transmit and receive (where the antenna elements 306 ₁-306 ₄ aresufficiently broadband to cover the different frequencies). In suchimplementations, different sets of coefficients for transmit and receivemay be used to achieve transmit and receive radiation patterns havingsubstantially similar directivity.

The use of a focal-plane array and associated circuitry may in amicrowave backhaul transceiver 120 enable a first microwave backhaultransceiver 120 to select one or more link partner(s) from a set ofsecond microwave backhaul transceivers. For example, the microwavebackhaul transceiver 120 a of FIGS. 6A and 6B is operable to selectbetween communicating with microwave backhaul transceiver 120 b via link602, communicating with microwave backhaul transceiver 120 c via link606, or communicating with both 120 b and 120 c via links 602 and 606.In this regard, a first set of beamforming coefficients may achieve aradiation pattern primarily directed at 120 b and a second set ofbeamforming coefficients may achieve a radiation pattern primarilydirected at 120 c. Factors which spatial routing algorithms implementedin the transceiver 120 a may take into account when deciding which ofthe links to transmit on and/or listen to include: atmosphericconditions, physical obstructions in the line-of-sight, performancemetrics (e.g., throughput, signal-to-noise ratio (SNR), packet errorrate, symbol error rate, bit error rate, latency, energy efficiency(e.g., bits per joule), destination of the data, and/or the like) of thelinks 602 and 606, and/or use of frequencies and airspace by othermicrowave backhaul transceivers. While any combination of these andother factors may be used by the spatial routing algorithms, FIGS. 6Aand 6B provide one example in which spatial routing is performed basedon atmospheric conditions and throughput, and FIGS. 7A-7C provideanother example in which spatial routing is performed based on backhaullink performance and latency.

For spatial routing based on destination of the data to be backhauled,the beamforming parameters may change along with the destination addressof data to be transmitted. For example, where the data is packetizedwith each packet containing a destination address, the parameters may bedetermined on a packet-by-packet basis. Similarly, where bursts ofpackets are backhauled, the parameters may be determined on aburst-by-burst basis.

In FIGS. 6A and 6B, it is assumed for purposes of illustration (and notlimitation) that the transceivers 120 b and 120 c are equidistant fromtransceiver 120 a and that line-of-sight between 120 a and 120 b is atthe same angle (relative to boresight of transceiver 120 a) as theline-of-sight between 120 a and 120 c. It is further assumed forillustration, that differences in throughput between links 602 and 606are due entirely to atmospheric attenuation (i.e., they use all the sameprotocols, signaling parameters, etc.).

Given the assumptions of the preceding paragraph, in FIG. 6A, whereskies are clear between transceiver 120 a and 120 b but there is rainbetween transceivers 120 a and 120 c, higher throughput is achievable onlink 602 than link 606. This results in the link 602 being selected forbackhauling data between nodes 608 and 610. Accordingly, the transceiver120 a configures its radiation pattern for communication withtransceiver 120 b. In FIG. 6B on the other hand, where the atmosphericconditions on the links are now reversed (e.g., as an isolatedthunderstorm has swept across the area) the link 606 offers higherthroughput. As a result, link 606 is selected for backhauling databetween nodes 608 and 610, and the radiation pattern of the transceiver120 a is configured accordingly.

In an example implementation, whichever of links 602 and 606 is notbeing used for backhauling data may still be kept active. For example,while backhauling data over link 602, the transceiver 120 a mayperiodically switch back to the link 606 just long enough to send and/orreceive pilots or other information for maintaining synchronizationbetween 120 a and 120 c. This may speed up the transition frombackhauling over link 602 to backhauling over link 606, thus introducingless latency in the data and requiring less memory for buffering. Thismay enable the spatial routing performed by the transceiver 120 a to betransparent to the nodes 608 and 610 (i.e., it makes no difference tothe nodes 608 and 610 whether data was received via 602 or 606).

In FIGS. 7A-7C there are shown four microwave backhaul transceivers 120a-120 d. For purposes of illustration (and not limitation) it is assumedthat transceiver 120 b is 1 km from transceiver 120 a at an angle of 0°,transceiver 120 c is 1.5 km from transceiver 120 a at an angle of +3°,and transceiver 120 d is 1.2 km from transceiver 120 a at an angle of−3°. For purposes of illustration, it is also assumed that each wiredhop in FIG. 7A-7C has the same latency and that the differences inpropagation time between the three backhaul links 702, 704, and 706 isnegligible.

In the clear weather conditions of FIG. 7A, the transceiver 120 a iscapable of communicating with transceiver 120 c at some minimumnecessary SNR. In FIG. 7A link 706 is selected for backhauling data fromnode 708 to node 714 as the total path consists of only three hops.Accordingly, the radiation pattern of transceiver 120 a is configuredfor backhauling the data to transceiver 120 c.

In the deteriorated atmospheric conditions of FIG. 7B, however, theminimum necessary SNR is no longer achievable on link 706 (706 being thelongest of the three backhaul links). Consequently, the transceiver 120a needs to select a different path. Since both links 702 and 704 canstill achieve the minimum SNR, transceiver 120 a is configured forbackhauling the data over link 702 since it consists of four hops asopposed to five hops for going over backhaul link 704.

In FIG. 7C, the atmospheric conditions have deteriorated again to thepoint where the minimum necessary SNR can no longer be achieved on link702. Accordingly, the transceiver selects link 704 and configures itsradiation pattern accordingly.

The routing may also include fiber links, cellular links, Wi-Fi links,and/or other channels available at one or more of themicrowave/millimeter-wave radio assemblies. For example, where none ofthe links 702, 704, and 706 can achieve the necessary minimum SNR, thetransceiver 120 a may backhaul the data over a cellular connection (notshown) that operates on frequencies relatively immune to atmosphericattenuation and/or or over a fiber connection (not shown). Using suchalternative connections for backhauling may be used only as a lastresort because of cost, for example (e.g., the owner of the backhaultransceiver 120 a has to pay the cellular provider or fiber provider).

In an example implementation, spatial routing by a microwave backhaultransceiver may be based on use of airspace and/or avoiding collisionswith other backhaul links. For example, referring to FIG. 8, the links802 between transceivers 120 a and 120 b may use the same frequenciesand intersect at line-of-sight intersection 810. The line-of-sightintersection 810 may, for example be determined from GPS coordinates andmounting heights of the transceivers 120 a-120 d. For example, whendeciding whether to backhaul data via link 802 or link 806, thetransceiver 120 a may determine whether there is likely to be data onlink 804 at the same time. This may be determined, for example, from acentralized service that schedules and/or monitors activity on thebackhaul link 810. Where, for example, link 802 is otherwise preferable,the transceiver 120 a may generally backhaul data over link 802 exceptwhen transmissions are occurring on link 810, in which case it maybackhaul data over link 806.

In an example implementation, the service may broker access to thefrequencies which are used on links having line-of-sight intersections.If the service indicates that the intersection is available at aparticular time, a license for using the frequencies in the intersectionat that particular time may be taken out for the amount of time needed(licenses may be available in second, minute, hour, or day increments,for example). Where two transceivers are vying for the same frequency ata particular location and particular time, bidding or some other form ofarbitration may be used to decide which transceiver gets the license.

In accordance with an example implementation of this disclosure, a firstmicrowave backhaul transceiver (e.g., 120 a of FIG. 6A) may comprise aplurality of antenna elements (e.g., 306 ₁-306 ₄). The transceiver maydetermine atmospheric conditions between it and one or more potentiallink partners, and adjust a radiation pattern of the plurality ofantenna elements based on the determined atmospheric conditions. A firstradiation pattern of the plurality of antenna elements may correspond toa first microwave backhaul link between the first microwave transceiverand the second microwave backhaul transceiver. A second radiationpattern of the plurality of antenna elements may correspond to a secondmicrowave backhaul link between the first microwave transceiver and thethird microwave backhaul transceiver. The transceiver may adjust theradiation pattern while maintaining one or more active microwavebackhaul links. The transceiver may adjust the radiation pattern basedon characteristics of data to be transmitted. The characteristics maycomprise a destination address of the data to be transmitted. Forbackhauling packets of data, the transceiver may adjust the radiationpattern on a packet-by-packet basis. The transceiver may store andupdate (e.g., continuously or periodically) a routing table havingentries associated with the second microwave backhaul transceiver andthe third microwave backhaul transceiver. The transceiver may adjust theradiation pattern based on the routing table. The transceiver may adjustthe radiation pattern to be the first radiation pattern when atmosphericattenuation between the first microwave backhaul transceiver and thesecond microwave backhaul transceiver (e.g., 120 b of FIGS. 6A and 6B)is less than atmospheric attenuation between the first microwavebackhaul transceiver and the third microwave backhaul transceiver (e.g.,120 c of FIGS. 6A and 6B). The transceiver may adjust the radiationpattern to be the second radiation pattern when the determinedatmospheric conditions are such that atmospheric attenuation between thefirst microwave backhaul transceiver and the second microwave backhaultransceiver is greater than atmospheric attenuation between the firstmicrowave backhaul transceiver and the third microwave backhaultransceiver. The transceiver may determine activity on a third backhaullink which intersects with the first microwave backhaul link, and adjustthe radiation pattern based on the determined activity on the link so asto avoid collisions between the first microwave backhaul link and thethird microwave backhaul link. The determining of the activity on thethird backhaul link may be accomplished by accessing a network servicethat maintains backhaul link activity information.

The present method and/or system may be realized in hardware, software,or a combination of hardware and software. The present methods and/orsystems may be realized in a centralized fashion in at least onecomputing system, or in a distributed fashion where different elementsare spread across several interconnected computing systems. Any kind ofcomputing system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computing system with a program orother code that, when being loaded and executed, controls the computingsystem such that it carries out the methods described herein. Anothertypical implementation may comprise an application specific integratedcircuit or chip. Some implementations may comprise a non-transitorymachine-readable (e.g., computer readable) medium (e.g., FLASH drive,optical disk, magnetic storage disk, or the like) having stored thereonone or more lines of code executable by a machine, thereby causing themachine to perform processes as described herein.

While the present method and/or system has been described with referenceto certain implementations, it will be understood by those skilled inthe art that various changes may be made and equivalents may besubstituted without departing from the scope of the present methodand/or system. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the presentdisclosure without departing from its scope. Therefore, it is intendedthat the present method and/or system not be limited to the particularimplementations disclosed, but that the present method and/or systemwill include all implementations falling within the scope of theappended claims.

What is claimed is:
 1. A system comprising: a first microwave backhaultransceiver comprising digital circuitry and beamforming circuitry,wherein: the digital circuitry is operable to determine a characteristicof data to be transmitted by the first microwave backhaul transceiver;the digital circuitry is operable to configure the beamforming circuitryto select one of a plurality of radiation patterns of a plurality ofantenna elements based on the determined characteristic of the data tobe transmitted; a first radiation pattern of the plurality of radiationpatterns corresponds to a first microwave backhaul link between thefirst microwave backhaul transceiver and a second microwave backhaultransceiver; and a second radiation pattern of the plurality ofradiation patterns corresponds to a second microwave backhaul linkbetween the first microwave backhaul transceiver and a third microwavebackhaul transceiver.
 2. The system of claim 1, wherein the digitalcircuitry and beamforming circuitry are configured such that the firstmicrowave transceiver is operable to switch between different radiationpatterns of the plurality of radiation patterns while maintaining one ormore active microwave backhaul links.
 3. The system of claim 1, whereinthe characteristic comprises a destination address of the data to betransmitted.
 4. The system of claim 1, wherein: the digital circuitry isoperable to select the first radiation pattern as the one of theplurality of radiation patterns when the destination address is a firstaddress; and the digital circuitry is operable to select the secondradiation pattern as the one of the plurality of radiation patterns whenthe destination address is a second address.
 5. The system of claim 1,wherein: the data to be transmitted is packetized; and the digitalcircuitry is operable to perform the determination and configuration ona packet-by-packet basis.
 6. The system of claim 1, wherein the digitalcircuitry comprises memory that stores a routing table having entriesassociated with the second microwave backhaul transceiver and the thirdmicrowave backhaul transceiver.
 7. The system of claim 6, wherein theconfiguration of the beamforming circuitry is based on the routingtable.
 8. The system of claim 1, wherein: the digital circuitry isoperable to determine activity on a third microwave backhaul link whichintersects with the first microwave backhaul link; and the digitalcircuitry is operable to select the one of the plurality of radiationpatterns based on the determined activity on the third microwavebackhaul link so as to avoid collisions between the first microwavebackhaul link and the third microwave backhaul link.
 9. The system ofclaim 8, wherein the digital circuitry is operable to determine theactivity on the third microwave backhaul link by accessing a networkservice which maintains backhaul link activity information.
 10. A methodcomprising: determining, by digital circuitry of a first microwavebackhaul transceiver, a characteristic of data to be transmitted by thefirst microwave backhaul transceiver; and configuring, by the digitalcircuitry, beamforming circuitry of the first microwave transceiver toselect one of a plurality of radiation patterns of a plurality ofantenna elements based on the determined characteristic of the data tobe transmitted, wherein: a first radiation pattern of the plurality ofradiation patterns corresponds to a first microwave backhaul linkbetween the first microwave backhaul transceiver and a second microwavebackhaul transceiver; and a second radiation pattern of the plurality ofradiation patterns corresponds to a second microwave backhaul linkbetween the first microwave backhaul transceiver and a third microwavebackhaul transceiver.
 11. The method of claim 10, wherein theconfiguring comprises switching from a second one of the plurality ofradiation patterns to the selected one of the plurality of radiationpatterns while maintaining one or more active microwave backhaul links.12. The method of claim 10, wherein the characteristic comprises adestination address of the data to be transmitted.
 13. The method ofclaim 10, comprising: configuring, by the digital circuitry, thebeamforming circuitry to select the first radiation pattern as the oneof the plurality of radiation patterns when the destination address is afirst address; and configuring, by the digital circuitry, thebeamforming circuitry to select the second radiation pattern as the oneof the plurality of radiation patterns when the destination address is asecond address.
 14. The method of claim 10, wherein the data to betransmitted is packetized, and the determining and configuring is doneon a packet-by-packet basis.
 15. The method of claim 10, wherein thedigital circuitry comprises memory that stores a routing table havingentries associated with the second microwave backhaul transceiver andthe third microwave backhaul transceiver.
 16. The method of claim 15,wherein the configuring of the beamforming circuitry is based on therouting table.
 17. The method of claim 10, comprising: determining, bythe digital circuitry, activity on a third microwave backhaul link whichintersects with the first microwave backhaul link; and performing, bythe digital circuitry, the configuring of the beamforming circuitrybased on the determined activity on the third microwave backhaul link soas to avoid collisions between the first microwave backhaul link and thethird microwave backhaul link.
 18. The method of claim 17, wherein thedetermining the activity on the third microwave backhaul link comprisingaccessing, by the digital circuitry, a network service which maintainsbackhaul link activity information.